Nine of ten nuclear reactors at two locations at Fukushima, Japan, have problems ranging from damaged cooling systems to partial meltdowns, and spent fuel storage facilities at several of these reactors are severely damaged. In some cases, facilities seem to have been shut down safely. In other cases, there is a strong suspicion of serious damage but the degree of damage is uncertain.Executive summary: The current most likely worst-case scenario is that the spent fuel rods in the storage pool at Reactor Number 4 will undergo a renewed chain reaction. However, two reactors, Number 1 and 3, may be partly melted, and the stored spent fuel rods at Reactor Number 3 contain a somewhat more dangerous fuel, Plutonium, as a percentage of their fissionable material.

A more detailed summary based on information from news sources in Japan:
At Fukushima Daini, Reactor Number 3 was shutdown after the quake and there appears to be no problem there. Reactors number 1, 2 and 4 at this location suffered cooling pump failures, and were shut down. Reported increases in radiation observed at this plant on March 14th were probably due to radiation coming from Fukushima Daiichi. There seems to be little information regarding the nature of the “cooling pump failures” at this plant, and information about the condition of the plant (i.e., what it will take to make it operable again) is not readily available.

At Fukushima Daiichi, Reactor Number 1 was operating at the time of the earthquake. The cooling system has failed and there appears to be a partial melting of the core. The reactor building suffered what appears to be a hydrogen explosion on Saturday, with the roof being blown off. Seawater is being pumped into this reactor to replace the function of the failed cooling system.
Reactor Number 2 was operating at the time of the earthquake. The cooling system here has failed and seawater is being pumped in to take over that function. The fuel rods in the core were fully exposed at one point. The building housing the reactor was damaged by an explosion at Reactor Number 3 on Monday. A second explosion was heard from within the reactor building on Tuesday, and it is believed that this may have involved damage to the reactor containment vessel.
Reactor Number 3 was operating at the time of the earthquake. The cooling system failed and seawater is being pumped in to take over that function. On Monday, a hydrogen explosion damaged the building housing the reactor. It is feared that the reactor has suffered a partial meltdown. High levels of radiation have been measured form this building.

A spent fuel storage pool at this site is compromised. Some of the fuel rods in this facility are said to be “MOX” fuel, which includes Plutonium and is considered to be a bit tricker to manage. A plume of smoke observed on Wednesday is suspected to have come from a fire in this pool, strongly suggesting a lack of water necessary to cool and shield the fuel rods. Various attempts have been made to get seawater into this pool, including dumping it form helicopters and spraying it from high pressure pumps. There is a fear that water poured in an uncontrolled manner into the pool could physically move the fuel rods to an undesirable position.

Reactor Number 4 was not in operation at the time of the earthquake. There is a spent fuel storage pool at this location that appears to be compromised. The temperature of water in this pool has been measured at unsafe levels and a series of fires have occurred. The fires have destroyed most of the building hosing the reactor and pool. Engineers have expressed concern that these fuel rods may restart a nuclear chain reaction.

Reactors 5 and 6 were under maintenance at the time of the earthquake. Both reactors have spent fuel rod pools, and both pools are showing higher than normal temperatures.

There is also a common spent fuel pond at which no problems have been reported.

re Daiichi 2 “The fuel rods in the core were fully exposed at one point.” is misleading: fuel is still in the reactor vessel, water level may have dropped enough to expose the rods in the reactor vessel, but the core is not directly exposed to the environment. re Daiichi report from the reactor operator indicates that fire was seen at the unit twice, but was out both times by the time crews arrived to put it out. Earlier report suggested fire may have been from small spill of lubricating oil?

@Geekzer – IAEA has raised the accident rating to 5 largely based upon core damage to reactors 1, 2 and 3. The “feared” hole in the suppression pool at no.2 would indeed expose the core to the environment.

There’s a blog going around on the internet that says among other things that there’s little need to worry about a meltdown at the Fukushima nuclear reactors because they have “core catchers”, that is a large shallow concrete basin that would catches the molten core and spread it out so that the chain reaction slows down.
However, they apparently don’t have core catchers, which were invented after these reactors were built.
There’s a good blog at http://mitnse.com by the MIT Nuclear Science and Engineering department, which helps to give a realistic idea of what is going on and the risks involved. All I’ve read suggests that the media is overplaying the nuclear problems since they are more interesting than mass homelessness and death from the tsunami.

This may not sound very scientific but hosing the fires or using buckets is likely to do little. For those of you who have been to a bon fire and tried to urinate on it may understand why. The water evaporates before it even touches the fire and what little does make it is instantly gone.

I guess dropping in some industrial generators or large pumps that have their own motors like those used to pump out flooded dikes or in hazardous liquid removable (often used in mills) are readily available and pump huge amounts of liquid through long lengths of hose. I guess I not there but I vote these guys are idiots and expect it to get worse.

I find it disturbing that the weather is causing rainout this can lower the radiation burden in the free air but it also concentrates the material on the ground. Depending on how they sample for radiation (airsampling versus ground surveys) the rainout could show an artificially low air reading. They have found pockets of concentrated radiation well outside the 30km exclusion zone. I’m shocked a technological giant like Japan doesn’t have the ability to survey radiation roboticly from the air.

Back in the days of atomic surface tests fallout was traveling across the US and was rained out across the country. On 4/27/53 a small group of university radiochemistry students at Rensselaer Polytechnic Institute noticed above background levels in their lab, when they surveyed outside they found the ground was very active in some places thousands of times above normal. Downspouts and puddles were especially active samples of puddle water showed a radioactive level of 270,000 micromicrocuries per liter the maximum level permitted by the AEC at the time was 100 mmc/l normal drinking water has 1 mmc/l. Professor Herbert Clark quickly guessed where the high readings had come from it had rained the evening before and an atomic bomb(Operation Upshot-Knothole shot Simon) had been set off two days earlier this was “rainout” a concentrated form of fallout.

Another problem with all the talk of “safe” levels of radiation is not all man made decay products are as benign as natural materials Uranium passes through the body radioactive Iodine and Cesium are incorporated into the tissues of all animals and plants

You raise the right questions, for which there are no good answers; certainly, there are no answers that support the view that ‘there is no reason for most people to worry’ (except, perhaps, for the heroic technicians and emergency responders working at Daiichi).

Damage to living organisms as a result of exposure to ionising radiation mainly occurs at the cellular level, and manifests itself in a variety of ways depending on the type of radiation, the radiation dose and the duration of exposure. The effects of being exposed to ionising radiation in humans range from:

• Skin burn, which occasionally manifests itself as a result of intense radiotherapy
treatment;
• Cancer, which includes skin cancer and leukaemia;
• Teratogenic effects, i.e. the impairment of an embryo in utero; and
• Blood destruction and death within days, for example when directly exposed to high doses of radiation as would be associated with the explosion of a nuclear weapon.

An important distinction when considering exposure to ionising radiation is between ‘prompt’ or ‘acute’ effects, and ‘delayed’ effects. Prompt effects are usually due to large exposures delivered over a short period of time, as would be the case in an explosion and fallout of a nuclear bomb, or a major accident in a nuclear reactor, and usually occur within hours or days following such exposure. Prompt effects are dose dependent or, more accurately, dependent on the total amount of energy transferred between the source of radiation and the receptor. Below a certain dose there is no discernible effect, but as the dose increases – all other things being equal – the magnitude and
manifestation of the effects also increase. As there is a direct relationship between the applied dose and the resulting effects, chance is not playing a part here; dose dependent effects are therefore also called ‘deterministic’ or ‘non-stochastic’.

Non-stochastic effects have exposure thresholds below which no health effects are observable, while increasing exposures to above such thresholds gives rise to physical effects which are reasonably predictable.

On the other hand, certain kinds of cancer are induced through the prolonged exposure to ionising radiation. Such effects may not occur immediately, or even within a short period following the exposure, or they may not occur at all. Because of the probabilistic nature of such delayed effects, they are also termed ‘stochastic’. No threshold exists for stochastic effects – an increase in radiation dose results in an increase of the likelihood of such effects occurring, but not of the severity of impacts.

Therefore, when considering the effects of prolonged exposures to low levels of ionising radiation, as would for example occur in a population living near uranium mining and milling operations, the possibility of having delayed stochastic effects constitutes the main health concern.

In contrast to non-stochastic effects, it is far more difficult to quantify low level exposure risks and identify exposure thresholds for stochastic effects. This is partly because of the ‘all or nothing’ nature of such effects, and because it is difficult to separate out the effects of low
level but prolonged radiation exposure from prevailing levels of natural background radiation. In addition, a variety of environmental effects, personal behaviour patterns (such as smoking and air travel) as well as the personal genetic predisposition all have an influence and
determine whether and how substantially a person is affected by low level exposure to ionising radiation.

The actual estimation of the health risk associated with exposures to low levels of ionising radiation is a complex process, which involves determining the type of radiation, duration of exposure and amount of energy actually deposited into particular organs. When exposed to
radionuclides it is important to determine the (radio)-activity of the radionuclides in question, the rate at which the body deals with and eliminates such radionuclides, and identify the target organ, i.e. the particular organ in which the radionuclides are preferentially deposited.

Another consideration when determining the health risk associated with ionising radiation is whether the exposure to such radiation is external, i.e. from the outside of the body as is the case for cosmic and terrestrial gamma radiation, or is internal, which occurs by way of ingesting radioactively contaminated food or water, or as a result of inhaling radioactive dust or gas. Occupationally exposed groups (e.g. workers in the uranium mining sector, or some hospital staff and airline personnel) tend to receive higher exposure doses over time than members of the general public.

When considering a total population’s health risks from radiation, human factors also assume importance. Effects due to the exposure to radiation are generally more serious in unborn babies and children.”

As radioactive materials disseminate through the environment (water, soil, plants, animals, air, etc.), greater numbers of individuals will face indeterminate exposure– some external, some ingested (as the residents of Tokyo, whose tap water is now shown to have increased levels of radioactivity).

What the ‘don’t worry’ crowd seems to downplay, is the cumulative nature of exposure, coupled with the idiosyncratic vulnerabilities of different individuals and cohorts (e.g., young children). The risks can be made to look trivial when washed across the whole population, and when each risk factor is considered in isolation.

I have a suspicion (maybe completely false, but I’ll gladly accept correction from a nuclear advocate), that when someone believes strongly that nuclear reactors are ‘generally safe’, there is a tendency to equate ‘low level exposure’ to ‘can be discounted from future consideration’. Stated differently– ‘this instance of exposure on this day with this person’ (they only ate half an ounce of contaminated spinach, and eight ounces of contaminated water), then those exposures don’t need to be counted towards the total.

The risks of exposure are cumulative, not discrete. It is somewhat misleading to make a statement ‘the dose was less than you might get from a dental X-ray’, with the implication that expressing concern is tantamount to an admission of ignorance, and unwarranted concern (mature, informed people, apparently, wouldn’t worry).

Since I’ve already gotten the dental X-rays, and my exposure from sunlight, and radon, and so forth, I’d rather not keep adding more exposures. Especially since this latest round of exposures for the people of Japan was entirely preventable. No reactor, no increased risk of exposure.

The inevitability of health effects among individuals is what makes the risks of nuclear power unacceptable. The myth of its basic safety relies on considering the risks in isolation, diluting the estimate of risks across populations, and ingnoring the cumulative nature of the risks. Oh, and highly favorable assumtions about likelihood of adverse events.

I am not a scientist & whilst I get the gist of what you say, I haven’t gained any idea of the implications of your worst case scenarios for people living in Japan.

For example, if “the spent fuel rods in the storage pool at Reactor Number 4 undergo a renewed chain reaction” AND there is unstoppable radiation from reactors 1 & 3 – including plutonium from 3 – what could the dangers be for people living 100, 200, 300 etc kilometers from the site, assuming the wind is blowing their way?

(I have friends in Japan whom I am trying to advise as to the potential dangers.)

Hi, thanks for your input. Please check the information of the CRIIRAD in France, there has been two communiqués stating that the data that is being collected by the 60 measuring labs around the world are being withheld from the States and confiscated from public awareness.

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